Environmental sensors, such as metal-oxide sensors, are often employed in a number of applications where the detection of various vapors or gases may be used to discern useful information. For example, environmental sensors may be utilized to monitor industrial areas for chemical or physical hazards, such as the detection of carbon dioxide within the chemical manufacturing industry, detection of engine exhaust gases such as carbon monoxide, hydrocarbons, and nitrogen oxides within the transportation industry, and detection of fugitive methane emissions within the oil and gas industry.
One technique for sensing such environmental changes is by employing a conventional sensor, such as a radio frequency identification (RFID) sensor, a resistance sensor, and/or a capacitance sensor coated with a particular sensing material. The impedance, resistance, capacitance response of the conventional sensor can be measured via inductive coupling or directly by connecting to a sensor reader. The electrical response of the conventional sensor is translated into the impedance, resistance, or capacitance changes of the conventional sensor, which is utilized to determine a concentration of a chemical vapor of interest, such as carbon dioxide, carbon monoxide, and nitrogen oxide, or methane gas. However, available conventional sensors suffer from a non-linear response, specifically an exponential, power law, and/or non-monotonic response, as a function of the chemical vapor concentration. Due to the power law response, as the concentration of the chemical vapor increases, the chemical vapor saturates the conventional sensor response leading to significant errors in estimation of the chemical vapor concentration. The terms “gas” and “vapor” describe any volatile species that are in contact with the sensor.
Additionally, conventional sensors are affected by other chemical vapors (e.g., not the chemical vapor of interest) exposed to the conventional sensor, such as a concentration of water vapor (e.g., ambient humidity). The water vapor shifts or saturates the response of the conventional sensor, which can affect a determination of the concentration of the chemical vapor of interest by the sensor.
The conventional sensors can be implemented in a conventional wireless sensing network (WSN) as sensor nodes. However, the sensor nodes within the conventional WSN are unable to measure multiple gases with individual sensors, reducing the reliability of the conventional WSN. Thus, conventional WSN require multiple conventional sensors for each sensor node. Each conventional sensor is configured to measure a specific gas. However, due to the plurality of conventional sensors for the sensor nodes, the sensor nodes demand a high power consumption, which restricts the type of power sources that can be utilized to power the node. Further, the high power consumption reduces the lifetime of the sensor nodes within the conventional WSN.